31P and 1H spectra have been obtained on intact isolated andsuperfused toad retinae. Up to eight retinae are studied in acommercial probe and a single retina is studied in a purpose-builtsmall-sample spectroscopy probe. Adequacy of tissue maintenanceconditions has been demonstrated. Differences in phosphorusmetabolite concentrations have been observed under conditions oflight and dark adaptation. Cyclic GMP has been demonstrated in the31P NMR spectrum of retina. Both 31P and 1H spectra are affected byaltering levels of calcium, a useful finding since calcium isthought to be involved in light